Thermostatic switch



April 7, 1953 c. s. MERTLER' THERMOSTATIC. SWITCH 2 Sl-IEETS-SHEET 1Filed Feb. 7, 1948 fie. 16

d- I 3Z 150 fie. 4

, INVENTOR. (mazes Silva-mew BY MM, 31 /41 3% p i 1953 c. s. MERTLER2,634,350

THERMOSTATIC SWITCH Filed Feb. 7, 1948 2 SHEETSSHEET 2 427 IN VEN TOR.

f/mzss .5. Mean 54 Patented Apr. 7, 1953 UNITED STATES PATENT OFFICE 1 4Claims.

This invention relates to thermostatic electricalswitches and moreparticularly to improvements in thermostatic switches which are of thetype commonly known as semisnap acting.

Thermostatic electrical switches known to the art may be classified inaccordance with their operational characteristics as being one of threemain types. One of these main types includes those switches which areknown as snap acting because they employ springs and/or levers tooperate at least one of the electrical contacts with a positive snapaction at the instant the thermal responsive member reaches apredetermined temperature. Switches of this type have the advantages ofhigh current carrying capacity, long contact life and absence of circuitdisturbances which cause interference with radio reception. However,such switches are relatively expensive to manufacture and possess aninherent wide temperature diiferential between the opening and closingoperating temperatures.

A second category of thermostatic electrical switches comprises thosewhich are known as the creep type because the electrical contacts areopened and closed relatively slowly under the sole influence of thebending of the thermal responsive member as the temperature thereofchanges. Switches of this type possess the advantages of low cost andrelatively small temperature differential but have relatively shortcontact life and cause considerable radio interference due to thefluttering and consequent frying of the contacts at the instant whenthey are either opening or closing. Moreover, the current carryingcapacity of'thermostatic switches of this type is of a relatively loworder since high currents intensify the above mentioned disadvantages.

The third general type of thermostatic switches comprises those known assemisnap acting. Switches of this type are somewhat similar inconstruction to the creep type but differ in operating principle in thatthe contacts open with a small snap action. This snap action resultsfrom disposing the thermal responsive member so that it is eiiective toexert both a frictional and a motion producing force upon a member whichmovably supports one of the switch contacts. The frictional forceenables the thermal responsive member to store up a certain amount ofmotion producing energy before any movement of the movable contactsupporting member occurs. When the stored energy is sufficient toovercome the frictional force the movable contact is actuated with asmall snap action and this mode of operation is effective in bothcontact opening and closing directions. Switches of this type combinethe desirable operating features oi both the creep and snap acting typethermostatic switches while retaining the relatively low cost of thecreep type switches but without the undesirable functioningcharacteristics of the latter.

The principal object of this invention is to provide improved semisnapacting thermostatic switches which are simpler and less expensive tomanufacture and which have a greater snap action than prior switches ofthe same type.

Another object of the invention is to provide improved thermostaticswitches each of which employs a thermal responsive member forcontrolling the movement of a movable contact of the switch, the thermalresponsive member comprising two portions extending at substantiallyright angles to each other and so disposed in the switch as to exertboth substantially perpendicular and longitudinal forces upon the membercarrying the movable contact, whereby flexing of the thermal responsivemember in response to temperature changes does not result in movementor" the movable contact until the flexing has stored sufficient energyin the thermal responsive member to overcome the static friction betweenthe latter and the member carrying the movable contact, whereupon thelatter and its contact are moved with a snap action relative to thenormally stationary contact.

A furtherobject of the invention is to provide improved thermostaticswitches of the type mentioned in the preceding object and in which thetwo portions of the thermal responsive member are integral parts of aunitary bimetallic strip or bar so that both portions of the thermalresponsive member flex in response to a temperature change therebyaccentuating the snap action of the movable contact.

A still further object of the invention is to provide an improvedthermal responsive member having two integral bimetallic portionsextending angularly with respect to each other and so shaped thatflexing of the member, in response to temperature changes causes the endof one of said portions to have an increased movement in a directionproductive of snap-like action of a movable member actuated thereby.

The invention further resides in certain novel features of constructionand combination and arrangements of parts, and further objects andadvantages thereof will be apparent to those skilled in the art to whichit pertains from the following description of the present preferredaesasso embodiment thereof, and certain modifications thereof, describedwith reference to the accompanying drawings in which:

Fig. 1 is a top plan view of an improved thermostatic switch constructedin accordance with this invention;

Fig. 2 is a side view, partly in elevation and partly in section, of theswitch illustrated in Fig. 1, the view being taken substantially on line2--2 of Fig. 1;

Fig. 3 is a top plan view of the present preferred. form of athermostatic switch constructed in accordance with this invention;

Fig. 4 is a side view, partly in elevation and partly in section, of theswitch illustrated in Fig. 3, the view being taken substantially on theline 44 of Fig. 3;

Fig. 5 is a detached end elevational view of the thermal responsivemember illustrated in Figs. 1 to 4;

Fig. 6 is a side elevational view of a modified form of thermalresponsive member suitable for use in thermostatic switches constructedin accordance with this invention;

Fig. 7 is a top plan view of another form of thermostatic switchconstructed in accordance with this invention;

Fig. 8 is a side view, partly in elevation and partly in section, of theswitch illustrated in Fig. '7, the View being taken substantially on theline 8-8 of Fig. '7;

Fig. 9 is a side view, partly in elevation and partly in section, of afurther form of thermostatic switch constructed in accordance with thisinvention;

Fig. 10 is a detached top plan view of the thermal responsive memberemployed in the form of switch illustrated in Fig. 9;

Fig. 11 is a top plan view of a still further form of thermostaticswitch constructed in accordance with this invention;

Fig. 13.

Fig. 15 is an end elevational view of the thermal responsive memberillustrated in Fig. 14 as viewed from the right-hand side of Fig. 14;

Fig. 16 is a side elevational View of yet another form of thermostaticswitch constructed in accordance with this invention;

Fig. 17 is a side elevational view, to an enlarged scale, of the novelthermal responsive member employed in the switch illustrated in Fig. 16;and,

Fig. 18 is an end elevational view of the thermal responsive memberillustrated in Fig. 17 as viewed from the right-hand side of Fig. 17.

Referring first to Figs. 1 and 2 of the draw- .ings, the improvedthermostatic switch illustrated therein comprises an elongated basemember 29 preferably formed of metal although other relatively rigidmaterials such as hard rubber, plastic or the like may be employed.Adjacent one end, the base member 20 is provided with an openingtherethrough in which is mounted an internally threaded sleeve 21 theexternal diameter of the sleeve being less than the opening through thebase member. As shown in Fig. 2, this sleeve has an outwardly extendingflange 22 adjacent one end, and between this flange and the adjacentface of the base member is positioned a plate or sheet 23 of insulatingmaterial. Surrounding the shank of the sleeve 2!, and resting upon theother face of the base member 2%, is an insulating washer 24, and uponthe washer 24, and surrounding shank of the sleeve 2!, is positioned aterminal member 25. The outer end of the sleeve 2! is peened over orotherwise deformed into engagement with the terminal member 25 to firmlyclamp the parts just mentioned to the base member 28. The terminalmember 25 is shown as provided with an outwardly extending lug having athreaded opening 28 therein for receiving a connecting screw to which anelectrical conductor may be attached. In place of this construction itwill be apparent that the terminal member 25 may be provided with othermeans for effecting connection to an electrical conductor.

Threaded through the sleeve 2! is the threaded shank of a contactsupporting member 27 one end of which extends beyond the flange 22 ofsleeve 2! and is provided with an axially extending bore in which isreceived a reduced cylindrical portion 28 of an electrical contact 29,the latter being formed of silver or other suitable material. In theillustrated construction, the portion 28 of the contact has a force fitwithin the bore to prevent displacement therefrom but it will beapparent that the contact 29 may be otherwise connected to the end ofthe member 21. The other end of the member 21, which is opposite to thatprovided with the contact 29, has a screw-driver slot or is otherwiseformed to facilitate engagement of a tool therewith for efiectingthreading of the member through the sleeve 2!. Hence, the position ofthe contact 29 relative to the base 20 may be readily adjusted, thecontact being maintained in its adjusted position by means of a lock nut3i threaded upon the member 27 and cooperating with the end of thesleeve 2|.

A movable contact 32, formed of silver or other suitable material,cooperates with the normally stationary contact 29 and is adapted to bemoved with respect thereto by virtue of being mounted on one end of aresilient member 33. The other end of the member 53 is provided with anopening through which extends the shank 34 of a mounting member,generally designated 35. This mounting member 35 has an outwardlyextending flange 35 adjacent one end upon which the resilient member 33rests, the shank 34 of the mounting member also passing through alignedopenings in a spacing collar 3'5, an insulating washer 38, a thermalresponsive member 39, an insulating washer to and the other end of theinsulating plate or strip 23, in the order recited. The portion of theshank 34, above the insulating plate 23, extends through an opening 5]in the base member 20, located adjacent the end of the latter oppositeto the end which is provided with the contact 29. The shank 34 alsoextends beyond the base member 20 and is provided with a terminal member42 between which and the base member 20 is interposed an in sulatingwasher 43. The outer end of the shank 35 is peened over or otherwisedeformed to firmly clamp the resilient member 33, the thermal responsivemember 39, the terminal member 42 and the several insulating spacingwashers and/or collars to the base member. The construction justdescribed is such that the thermal responsive member is mounted invertical alignment between the base and resilient members 33 but spacedand insulated therefrom. The resilient member 33 normally extendssubstantially parallel with the base member 23 and is electricallyconnected, through the shank 34 of the mounting means, to the terminalmember 42 which preferably is provided with a threaded opening 44 toreceive a connecting screw for attaching an electrical conductorthereto.

The thermal responsive member 33 employed in the form of the improvedthermostatic switch illustrated in Figs. 1 and 2 comprises a unitarybimetallic strip or bar bent to provide two integral portions, a mainportion 39a and an ex= tension 3%, which are disposed at substantiallyright angles with respect to each other so that the main portionnormally extends substantially parallel with the base and the resilientmemhere 33 while the extension 39b is directed towards and issubstantially perpendicular to the resilient member 33.

As is well known in the art, the thermal responsive member 33 isconstructed of two pieces of metal having different coemcients ofexpansion and welded together so that variations in the temperature ofthe member causes flexing or bending thereof. In the form of the membershown in Figs. 1 and 2 the metal having the lower coeflicient ofexpansion is disposed adjacent the resilient member 33 so that anincrease in temperature causes the member to flex or bend from theposition shown in full lines in Fig. 2 to that indicated in broken linesin the same figure. The switch may, therefore, be employed wherever itis desired to control an electric circuit in accordance with the ambienttemperature of the location in which the switch is placed, the Iconstruction being such that the circuit extending from the terminal 25to the terminal 42 is closed through engagement of contacts 23 and 32when the temperature is below a certain predetermined value, contact 32being held in engagement with the contact '29 at such times by theresilient member 33. As the ambient temperature increases the thermalresponsive member 39 flexes to engage the resilient member 33 and thusdisengages the contact 32 from the contact 29 interrupting the circuittherethrough, the disengagement being eifected with a snap action ashereinafter described. As the ambient temperature drops, the thermalresponsive member returns to substantially its initial position thusreclosing the contacts 29 and 32, this movement of the contact 32likewise being effected with a snap action.

As mentioned above, the switch illustrated in Figs. 1 and 2 operateswith a snap action. This is due to the fact that the flexing or bendingof the thermal responsive member 39 results in the free end of thelatter moving substantially in an arc intersecting the resilient member33 so that the thermal responsive member exerts force upon the resilientmember in a direction which is substantially perpendicular to thatmember and also in a direction substantially parallel with thelongitudinal extent of the resilient member 33. This will be readilyunderstood from a consideration of Fig. 2 in which it will be seen thatthe initial movement of the thermostatic member, from the full lineposition to the broken line position, simply brings the free end of theextension 39b into engagement with the resilient member 33, the extentof this movement being determined by the adjusted position of thecontact 29 and the dimensions of the various parts employed intheswitch. A further increase in the ambient temperature causes thethermal responsive member to further flex thus exerting a force upon theresilient member 33 substantially perpendicular thereof as indicated bythe arrow A. Simultaneously the end of extension 391), which is now inengagement with the resilient member 33 tends to move longitudinallythereof in the direction indicated by the arrow 13 thereby producingfriction between the end of. extension 39b and the surface of the member33. Due to the well known fact that static friction exceeds slidingfriction, the end of the extension 39b is momentarily prevented fromfurther movement so that the contacts 29 and 32 remain in engagementwhile the further bending or flexing of the thermal responsive member 39increases the energy stored therein. When this stored energy issufficient to overcome the static friction, the end of the extension 3%slips over the surface of the resilient member 33 the initial portion ofthis movement being effected in a relatively short interval due to theenergy stored in the thermal responsive member. Consequently, theresilient member 33 and its contact 32 are moved downwardly as shown inFig. 2 with a snap-like action thus rapidly disengaging the contact 32from the contact 29.

The snap action just described is greater than that obtained withconventional constructions because the extension 3912 has an appreciablelength and since this extension, as well as the main body 33a of thethermal responsive member, is bimetallic it likewise flexes withvariations in temperature thereby increasing the extent of longitudinalmovement of the end of the extension along the resilient member 33.Consequently, the desired snap action is obtained with a lessertemperature differential than has heretofore been possible or,conversely, a wider contact separation results when an equivalenttemperature differential occurs. In view of the fact that frictionbetween two members is proportional to the areas of the surfaces inengagement, the thermal responsive member 39 is of substantial width andthe free end of extension 3% is preferably substantially rectangular asindicated in Fig. 5, the corners of this free end being preferablycurved slightly, however, so that a slight cooking of the thermalresponsive member will not result in a substantiall point contact withthe resilient member 33. If less static friction, and hence a smallerdegree of snap action is desired, the radius of curvature of the cornersof the free end of extension 39b may be increased thereby lessening thearea of the bimetal member which contacts the resilient member 33. Thedegree of snap action may also be varied by altering the pressureexerted by contact 32 upon contact 29 since this will vary the staticfriction which must be overcome in effecting switch operation. As shownin Fig. 2, the length of the extension 3912 is in the order of one-thirdthe length of the main portion 39a. This relationship of the lengths isnot, however, critical and may be varied so long as the extensionportion has an appreciable length suflicient to permit flexing thereof.

After the resilient member 33 has been moved, as just described, toseparate the contact 32 from contact 29, the parts are held in thisposition by the thermal responsive member until the ambient temperaturedrops below a predetermined value.

As the temperature drops the thermal responsive member tends to returnto its initial position. 'As before, however, static friction is presentbetween the end of the extension 3% and the resilient member 33 so thatmovement of the member 33 and contact 32 does not occur as soon as thethermostatic member begins to straighten,

" such movement occurring only after the thermal responsive member hasdropped sufiiciently in temperature so that the forces tending tostraighten it are sufiicient to overcome this static friction. When thispoint is reached there is a rapid relative movement of the end ofextension 3912 with respect to the resilient member so that the contact32 reengages contact 29 with a snap action.

The switch construction shown in Figs. 1 and 2 'may be used as asettable thermostatic switch for operation at diiferent temperatures bybacking off the nut 3| sufiiciently to permit easy adjustment of thethreaded contact supporting member 2?, Normally, however, the switchillustrated in Figs. 1 and 2 is intended for use only at a singlepredetermined temperature and hence the nut 3| is tightened to preventmovement of contact '29 after the latter has been initially adjustedvided with an opening I2I for receiving the reduced diameter shank of acontact mounting stud I22, which shank also passes through a plate orsheet of insulating material I23 and an insulating washer I23 which aredisposed on opposite sides of the base I20 to insulate the stud from thebase, it being understood that the shank of the stud has a diameterwhich is materially less than the diameter of the opening through thebase. Resting upon the insulating washer I24, and surrounding the shankof the stud I22, is a terminal member I25 provided with a threadedopening I26 for receiving a screw by which an electrical conductor maybe connected to the terminal member. The outer end of the stud I22 ispeened over or otherwise deformed, as indicated at I2'I, to rigidlysecure the stud and terminal member to the base I20 as shown in Fig. 4.The lower end of the stud I22 is provided with a contact surface I28which may be a layer of silver or other suitable material secured to theend of the stud in any suitable manner.

Cooperating with the contact I28 is a movable contact I29 of silver orother suitable material which is mounted on the outer end of a resilientmember I30. Disposed between the base I23 and the resilient member I33is a thermal responthe base I20, the members I30 and I3I being separatedby a collar I33 and an insulating washer I34, while the thermalresponsive member I3I is separated from the base I20 by an insulatingwasher I35, a collar I36 and a portion of the insulating plate or sheetmember I23. One end of the mounting means or stud is provided with anenlarged outwardly extending flange I37 forming a head for engagementwith the resilient member I30, the other end of the mounting meansextending beyond the base I20 and being provided with a terminal memberI38, insulated from the base I20 by an insulating washer I33, this endof the mounting means being peened over to rigidly secure the severalparts lust mentioned to the base I20. The terminal member I38 isprovided with a threaded opening I33! to receive a screw by which anelectrical conductor may be attached to the switch.

In order to provide for adjustment of the switch for operation atdifferent temperatures, the base member I20 intermediate its ends isprovided with a central opening surrounded by an integral, upstandingboss or sleeve I40 which is internally threaded and threadingly receivesthe threaded shank of an adjusting member Ill. The lower end of theadjusting member MI is preferably provided with a button I42 ofinsulating material and the sleeve or boss I40, together with theadjusting member I3I, are preferably so located that the button I42engages the thermal responsive member substantially intermediate theends of its horizontal portion I 3Ia. The member It! may be actuated bymeans of a knob or the like, not shown, provided thereon, the extent ofadjustment being limited by providing the member It! with a radiallyextending projection I33 which is adapted to abut a projection I03extending upwardly from the boss :53 and preferably formed integrallytherewith. It will be readily understood that by rotating the member It!the thermal responsive member I3I may be deflected to bring the free endof its extension portion I3Ib to any desired position relative to theresilient contact carrying member I30 thereby selecting the operatingtemperature for the switch.

The thermal responsive member I3I, shown in Figs. 3 and 4, is identicalwith that shown in Figs. 1 and 2 and operates in the same manner toeffect opening and closing of the contact I23 with respect to thecontact l28, the contact 29 being moved by a snap action as waspreviously described for the contact 32. In the present construction,however, the insulator button I42 on the adjustment member I3I forms anabutment for the main body portion I3Ia of the thermal responsive memberthus limiting the extent this portion can flex in an upward direction asviewed in Fig. 4 and thereby determining the temperature at whichcontact separation occurs.

The thermal responsive members illustrated in Figs. 1 to 4 are eachformed from a bimetallic strip or bar bent to provide two portionsextending at substantially right angles to each other the radius ofcurvature at the bend being relatively small. This radius of curvature,may, however, be increased without altering the operations of theswitches. Thus, Fig. 6 illustrates a bimetallic member which may beemployed in the switches illustrated in the Figs. 1 to 4 and willoperate in the same manner as the bimetal lic members illustratedtherein. This thermal responsive member, designated generally I50, isconstructed of a bimetallic strip or bar, one end of which is providedwith an opening I5I therethrough for receiving a mounting means such asthe shank 34 or I32 of the mounting members illustrated in Figs. 2 and4. The other end of the member I50 is bent on a relatively large radiusto provide an extension l50b which is disposed at substantially rightangles to the main body portion l5lla. This thermal responsive memberwill operate in the switches shown in the Figs. 1 to 4, to eiiect thepreviously mentioned snap action of the movable contact, by lesseningthe radius of curvature of the extension Gb as the temperature of thethermal responsive member rises, the operation being otherwise the sameas that previously described for the thermal responsive members 39 andHi.

Figs. '7 and 8 illustrate still another form of thermostatic switchconstructed in accordance with this invention, this form of switch beingsubstantially like that illustrated in Figs. 3 and 4 but diireringtherefrom primarily in the type of thermal responsive member employed.As illustrated, this form of switch comprises a base 220 adjacent oneend of which is mounted a relatively stationary contact 221 provided onthe lower end of a stud 222, the stud being connected to a terminalmember 223 and insulating members 224 and 225 being provided on eitherside of the base 223 in the same manner as are the corresponding partsshown in Fig. 4. Cooperating with the stationary contact 22| is amovable contact 226 mounted adjacent one end of a resilient member 221.The other end of the resilient member 221 is mounted in vertical spacedalignment with the base and a thermal responsive member 228 by a headedmounting member or stud 229 the shank of which passes, in order, throughopenings in the resilient member 221, spacing collar 230, insulatingwasher 23I, thermal responsive member 228, insulating washer 232,insulating member 224, the base 220, insulating washer 233 and terminalmember 234. The end of the mounting member or stud 229 is peened overabove the terminal member to rigidly mount the assembly just describedupon the base 22!] thereby providing an electrical connection betweenthe terminal 234 and resilient member 221 while insulating the mountingmember and the thermal responsive member from the base and from eachother. If desired, the insulating washer 232 may be replaced by asuitable spacer if greater separation is desired between the base andthermal responsive member 228.

The base 220 is also provided with an opening therethrough surrounded byan upstanding boss or sleeve 235 which is internally threaded to receivethe threaded shank of an adjusting member 236, the lower end of thelatter being provided with an insulating button 231 for engagement withthe main body portion 228a. of the thermal responsive member to therebyadjust the switch for operation at different predetermined temperatures.As before, the adjusting member 236 is preferably provided with aradially extending projection 238 for cooperation with an upstandingaxial projection on the sleeve or boss 235 and thereby limit the extentof rotative movement of the adjusting member 233.

'In the form of switch illustrated in Figs. 7 and 8 the thermalresponsive member 228 is shown as constructed of a main body portion228a formed from a bimetallic strip or bar which preferably taperssomewhat from its mounted endtowards it forward or free end. Thisforward or free end of the main body portion 228a provided with aprojection or pin 2281) which ell 10 extends at substantially rightangles from the main body portion 228a and is connected therewith so asto constitute an extension of the thermal responsive member.

The operation of a switch thus constructed is substantially similar tothat of the switches previously described and hence need not be furtherset forth in detail, it being sumcient to note that snap action is againprovided by the static friction developed between the end of extension2281) and the resilient member 221 when the bimetallic main body portion228a flexes in response to variations in temperature. In the instantconstruction, however, the extension 2281) is not bimetallic and hencedoes not itself flex. Therefore, the extent of longitudinal movement ofthe end of this extension along the resilient member 221 is less than inthe case of the bimetallic extensions of the previously describedthermal responsive members and hence the snap action and/or extent ofcontact separation is lessened.

Figs. 9 and 10 show still another form of thermostatic switchconstructed in accordance with this invention and which is in a largepart constructed substantially like the switches described withreference to Figs. 3 to 8. That is to say, the switch comprises a basemember 320 on which a stationary contact 321 is mounted and connectedwith a terminal member 322, the contact and terminal members beinginsulated from the base by insulating washers or members 323 and 324 asin the forms illustrated in Figs. 4 and 8.

Cooperating with the contact 321 is a movable contact 325 mounted on oneend of a resilient member 323. The other end of this resilient member isrigidly mounted upon the base 320 by a headed mounting means or stud321, the shank of which passes through an opening in the resilientmember 323 and through an opening in the base 320 as in the previouslydescribed constructions. As before, the mounting means or stud 321supports and engages a terminal member 328, the latter being insulatedfrom the base by an insulating washer 329, an electrical connectionbeing provided by the terminal member 328 through the mounting member321 to the resilient member 326 and thence to the contact 325.

A thermal responsive member 330 is disposed between the base 323 and theresilient member 326. This thermal responsive member is formed from abimetallic strip or bar one end of which is bent at substantially rightangles to the main body portion 333a thereby providing an extension3301: directed towards the resilient member 323. The other end of thethermal responsive member is provided with a substantially arcuateopening 33f, the member having oppositely disposed integral ears 332 and333 extending radially inwardly of this opening. These ears 332 and 333are received in cooperating recesses provided adjacent the upper surfaceof a spacing collar 333 which is mounted upon th mounting member or stud321, a space being provided between the spacing collar and the arcuateopening in the bimetal member as clearly shown in Fig. 10. Hence, thethermal responsive member 333 is hingedly connected to the base memberthrough the agency of the ears 332, 333, collar 33-1 and mounting member321, the ears 332, 333 being retained within their recesses by asuperimposed collar member 335 provided upon the mounting member 321between the collar 334 andthe insulating member 324. This form ofthermostatic switch also employs an adjusting means comprising athreaded member 335 which is threadedly received in a boss or sleeve 33?surrounding an opening extendin through the base 328. The end or theadjusting mean is provided, as in the previously described construction,with an insulating button 333 for engagement with the thermal responsivemember 333, the extent of adjustment being limited by abutment memberscarried upon the adjusting member and the boss or sleeve, respectively.

The form of switch illustrated in Figs. 9 and 10 operates in the samemanner as that illustrated in Figs. 3 and 4 and, hence need not befurther described. In the instant form of switch, however, adjustmentor" the thermal responsive member 338, to effect switch operation at apreselected temperature, does not involve any bending of the thermalresponsive member adjacent its mounting so that no stresses areintroduced therein by varying the setting at which the switch willoperate. This makes for longer life and at the same time avoidsintroducing stresses which might affect accurate operation of theswitch. Th movable contact 325 is, nevertheless, actuated with a snapaction in this type of construction since the insulating button 338provides an abutment limiting the extent that the portion 333a of thethermal responsive member can move in an upward direction, as viewed inFig. 9, so that flexing of this main body portion and of the extension3331) are effective, as in the previously described construction, toactuate contact 325 with a snap action.

Each of the switches heretofore described is so constructed thatincrease in temperature effects contact separation, the contacts beingnormally held in engagement by the biasing action of the resilientmember which carries the movable contact. The basic principles of thisinvention may, however, be embodied in a switch in which the movablcontact is so mounted as to be biased away from engagement with astationary contact, the contact being held in engagement by a thermalresponsive member in its cold position and allowed to open with asemisnap action under the control of the thermal responsive member whenthe temperature of the latter rises above a p e mined value. Such aswitch is illustrated in Figs; 11 and 12.

The switch illustrated in Figs. 11 and 12 comprises a base 420 having anopening therethrough for receiving a threaded portion of a mounting stud421 which forms a common mounting means for the various elements of theswitch. This is effected by providing the base 420 with an integralsleeve 422 which rigidly interconnects the various parts of the switch,the stud 42! passin therethrough and thereby connecting the switchelements to a supporting surface 45!]. The base 423 rests upon thesurface 453 and adjacent to this base the sleeve 422 is provided athermal responsive member 423, an insulating sleeve 424 being providedbetween the shank of the sleeve 422 and the -open ing through thethermal responsive member, and insulating washers 425 and 423 beinprovided on opposite sides of the thermal responsive member to insulatethe latter from the sleeve. One of the contacts 42'! of the switch ismounted upon the outer end of a resilient arm or member 428- the innerend of which is disposed about the insulating sleeve '424'and is spacedfrom the insulating washer 426, and hence from the thermal responsivemember 423, by a spacing collar 429. A terminal member 430 alsosurrounds a portion of th insulating sleeve 424 and rests upon theadjacent end of the resilient arm 423 thereby providing electricalcontact between these members, the outer end of the terminal member 436being provided with suitable means for connecting an electricalconductor thereto.

The second contact 43! is mounted on the outer end of a resilient switcharm or member 432 the inner end of which is supported invertical spacedrelationship with respect to the resilient member 428 by an insulatingwasher 433 and a terminal member 434, the resilient arm 432 and theterminal member 434 being insulated from the shank of th sleeve 422 byan insulating sleeve 435. The resilient arm 432 and terminal member 433being in contact with each other thereby provide a path for electricalcurrent from contact 43! through the resilient member 432 and to aconductor attached to the outer end of the terminal member 434.

A rigid arm 435 is mounted in vertical alignment with respect to thethermal resp nsive member 423 and resilient members 428 and 432 byhaving its inner end apertured and positioned about the sleeve 422, thearm 436 being spaced from the resilient member 432 and insulatedtherefrom by a spacing collar 43! and an insulating washer 438. Thethermal responsive member 433, resilient members 428, 432 and the arm436 are rigidly held together by spinning or otherwise deformin the endof the sleeve 422 into engagement with the upper surface of the arm 436,as shown in Fig. 12, so that the entire switch assembly may be readilyattached to or removed from a supporting surface, such as 450, by meansof the threaded stud 42 I.

The arm 436 is provided with an opening therethrough, adjacent its freeend, and surrounding this opening is an upstanding boss or sleeve 439internally threaded to receive the threaded end of an adjusting screw440. The lower end of the adjusting screw is provided with an abutmentbutton 44i of insulating material which is adapted to engage theresilient arm 432 intermediate its ends to thereby effect adjustment ofthe switch operation. The adjusting member 440 is provided with aradially outwardly extending projection 44! adapted to abut an upwardlyextending projection 442, which may be formed as as integral part of thearm 436, thereby providing means for limiting the amount of adjustmentof the switch. While the contact 43l is shown as mounted upon aresilient arm or member 432 this resiliency is provided primarily forease in eflecting adjustment of the switch and it will be understoodthat for any adjusted position the contact 43I is substantiallystationary.

The resilient arm 428 biases the movable contact 421 in a direction toeifect disengagement of the latter from the relatively stationarycontact 43! but the contacts are held in engagement, at

all temperatures below a predetermined value, by

tension 423b, extending substantially perpendicular to the arm or member428. This form of thermal responsive member is, therefore, generallysimilar to that shown in Figs. 1 through 4 but diifers therefrom in thatthe metal having the lower coefiicient of expansion is disposed on theouter side of the thermal responsive member in the form thereof shown inFig. 12. Hence, when the ambient temperature is below a predeterminedvalue, the thermal responsive member occupies the position indicated infull lines so that the contacts 12? and 531 are in engagement thuscompleting the electrical circuit therethrough. Upon an increase in theambient temperature, however, the thermal responsive member flexes orbends to the position shown in broken lines in Fig. 12 thereby effectingdisengagement of the contact 421 from contact 43! and interrupting theelectrical circuit therethrough. Operation of the contact 421 to andfrom engagement with contact 431 is, as in the previously describedembodiments of the switch, effected with a snap action due to thepeculiar construction of the switch by virtue of which the outer end ofextension 123b exerts both perpendicular and longitudinal forces uponthe resilient member 428. As mentioned in detail above, this results increating friction between the end of extension 423i) and the resilientmember 428 which prevents movement of the end of the extension over theresilient member, and hence prevents movement of the resilient memberand its contact, until sufficient energy has been stored in the thermalresponsive member to overcome the static friction whereupon actuation ofthe contact 42; is effected with a snap action.

Fig. 13 illustrates yet another form of thermostatic switch constructedin accordance with this invention, this form of switch beingsubstantially like that illustrated in Figs. 3 and 4 but differingtherefrom primarily in the type of thermal responsive member employed.As illustrated, this form of switch comprises a base 52 3, adjacent oneend of which is mounted a relatively stationary contact 52 I, providedon the lower end of a stud 522, the stud being connected to a terminalmember 523 and insulating members 524 and 525 being provided on eitherside of the base 523 in the same manner as are the corresponding partsshown in Fig. 4. Cooperating with the stationary contact 52l is amovable contact 526 mounted adjacent one end of a resilient member 52'!which normally biases the contact 526 into engagement with the contact52 l. The other end of the resilient member 521 is mounted in verticalspaced alignment with the base and a thermal responsive member 528 by aheaded mounting member or stud 529 the shank of which passes in orderthrough openings in the resilient member 521, spacing collar 53!],insulating washer 53 l, thermal responsive member 528, insulating washer532, spacing collar 533, insulating member 524, the base 520, insulatingwasher 534 and terminal member 535. The end of the mounting member orstud 529 is peened over above the terminal member 535 to rigidly mountthe assembly, just described, upon the base 520 thereby providing anelectrical connection between the terminal 535 and resilient member 521while insulating the mounting member and the thermal responsive memberfrom the base and from each other.

The base 523 is also provided with an opening therethrough surrounded byan upstanding boss or sleeve 533 which is internally threaded to receivethe threaded shank of an adjusting member 531, the lower end of thelatter being provided with an insulating button 538 for engagement withthe main body portion 528a of the thermal responsive member to therebyadjust the switch for operation at different predetermined temperatures.As before, the adjusting member 531 is preferably provided with aradially extending projection 539 for cooperation with an upstandingaxial projection on the sleeve or boss 536 to thereby limit the extentof rotary movement of the adjusting member 531.

The thermal responsive member 528, which is shown per se to an enlargedscale in Figs. 14 and 15, is formed of a bimetallic strip or bar, themetal having the higher coefiicient of expansion being disposed on thatside of the member which is adjacent the insulating button 538. One endof the main body portion 528a is provided with an opening therethroughto receive the shank of the stud or mounting means 529. The other end ofthe main body portion is bent to a substantially invertedJ-configuration, as shown in Figs. 13 and 14, thereby providing anextension or leg 52% which extends substantially at right angles withrespect to the main body portion 523.

The operation of the switch thus constructed is substantially similar tothat of the switches previously described and hence need not be furtherset forth in detail, it being sufiicient to note that snap action isagain provided by the static friction developed between the end of theextension 528i) and the resilient member 527 when the member 528 flexesin response to variations in temperature. In the instant construction,however, this snap action is enhanced over that provided by the thermalresponsive members illustrated in the other forms of switches. Ihis isdue to the fact that, since the entire thermal responsive member isformed from a unitary bimetallic strip or bar, it flexes throughout itsentire length in response to changes in temperature. That is to say, themain body portion 528a and the leg or extension 5281) both flex inresponse to changes in ambient temperature and, in addition, the curvedportion of the member has its radius of curvature altered by flexingthereof thus increasing the movement of the end of the extension 5253bin a direction which exerts longitudinal force upon the resilient memberor arm 52?. Consequently, the substantially longitudinal movement of thefree end of the thermal responsive member with respect to the resilientmember is considerably increased and, since it is this movement whichproduces the snap action, it will be apparent that a thermal responsivemember of this configuration is highly desirable where a relativelylarge snap action is desired. It will be apparent that the curvedportion of the thermal responsive member here illustrated may be alteredfrom that shown in Figs. 13 and 14, if desired. For example, the radiusof curvature may be greater or smaller than that indicated in thedrawings. Furthermore, this extension portion may be substantiallyU-shaped rather than substantially J-shaped, if desired, in which eventthe main body portion 528a would then be located more closely adjacentthe resilient member 521 in a switch constructed substantially as shownin Fig. 13, the collar 539 then being replaced by one having a lesserthickness.

Fig. 16 illustrates still another form of thermostatic switchconstructed in accordance with this invention. This form of switchcomprises a base 629 which may be constructed of any suitable materialbut is here shown as formed of an insulating material such as porcelainor the like. It

ass-43cc will be readily understood, however, that a metal base may beemployed together with suitable insulating washers as in the prior formsof switches. Adjacent one end of the base cze is mounted a relativelystationary contact 62! provided on the lower end of a stud 622, theshank of the stud passing through an opening in the base member 628 andan opening in a terminal member 623 and the latter member, as well asthe contact, being secured in place upon the base by deformation of theend of the stud as in the previous forms of the switches illustrated.Adjacent its head, the stud 622 is provided with a thermal responsivemember, generally designated 62d, one end of which is provided with anenlarged opening through which the shank of the stud 622 passes with aclearance. An insulating washer 625 is provided between the thermalresponsive member and the head of the stud 622, and a similar insulatingwasher B26 is provided between the other side of the thermal responsivemember and a spacing collar 62'! which provides the desired spacingbetween the thermal responsive member and the base.

The thermal responsive member 624, illustrated in Figs. 16, 17 and 18,comprises a main body portion 624a and an integral extension 6262), thesaid extension including a portion extending adjacent the said mainportion and united thereto by a substantially U-shaped curved portion6240, the free end 624d of the extension being bent at an angle withrespect to the main portion so as to be disposed at substantially rightangles with respect to the main portion and directed away from thelatter, see Figs. 16 and 17. This thermal responsive member isintegrally formed of bimetallic material and is adapted to flex, whensubjected to variations in ambient temperature, in a manner such thatthe free end 624d of the extension 62 3?) moves relative to the mainportion 822a in a direction having components extending bothsubstantially perpendicular to and sub-stantially parallel with the mainportion as in the previously described forms of thermal responsiveelements. In a thermal responsive member having the presentconfiguration, however, the latter component is increased.

The free end 62% of the thermal responsive member is disposed adjacent acontact supporting member 628, one end of which is provided with acontact 629 movable to and from engagement with the contact 52 I. Thismovable mounting is effected in the instant embodiment by forming thesupporting member 628 from flexible or resilient material such as thinmetal, or the like, and. supporting the end thereof, which is oppositeto that provided with the contact era, in a manner such that the contact629 is biased into engagement with contact 62!. The illustrated mountingfor the movable contact supporting arm 628 is similar to that in thepreviously described forms of switches and comprises a headed stud 638which passes serially through the contact supporting arm 628, a spacingcollar 63L base 62% and a terminal member 532, the outer end of the studbeing peened or otherwise deformed to rigidly secure together the partsjust mentioned.

In order to effect adjustment of the operation of a switch of the typejust described, a means is provided for adjusting the position of themain portion 624a of the thermal responsive member relative to the baseand to the movable contact supporting arm 628. This adjusting means maytake any desired form but is here illustrated as being similar to thosepreviously described with respect to Figs.'3, 4, 8, 9, 12 and 13. Thatis to say, the base 626 is provided with a suitable aperture throughwhich extends a threaded adjusting shaft 333, theouter end of which maybe provided with a knob or other means for effecting rotation thereof.The shaft 633 has a threaded engagement with a sleeve-like member 634which surrounds the aperture through the base and is connected with thelatter in any suitable manner. Adjustment of the shaft or screw 533 islimited by providing a radially extending projection 635 thereon whichis adapted to abut an axially extending projection 63B upon the sleeve634. The lower end of the adjusting screw or shaft 633 is provided withan abutment member or button 53! which may be formed of insulatingmaterial if so desired. This abutment member or button engages the mainportion of the thermal responsive member 62d relatively close to itsmounted end so that the freely flexing portion of the thermal responsivemember represents a majority of the entire length of the member.

The operation of this form of switch is substantially similar to theoperations of the previously described switches, since flexing of thethermal responsive member, in response to variations in temperature,cause the outer end 624a of the extension 6242) to engage the movablecontact supporting arm 628 and exert forces thereon in directions bothsubstantially perpendicular and longitudinal with respect thereto. As inthe prior forms of switches, the longitudinal force creates frictionbetween the free end of the thermal responsive member and the movablecontact supporting arm and hence no movement of said movable contact armoccurs until sumcient energy has been stored in the thermal responsivemember, by the flexing thereof, to overcome the static friction betweenit and the movable contact arm at which time the latter is moved with asnap action. The peculiar configuration of this form of thermalresponsive member, which for purposes of brevity may be referred to assubstantially hairpin shaped with one leg thereof shorter than theother, increases the amount of longi tudinal movement of the free endthereof so that greater snap action may be achieved with thev sametemperature diiferential or equivalent snap action may be achieved witha smaller temperature difierential.

While a number of different embodiments of switches, constructed inaccordance with this invention, have been illustrated and described indetail it will be readily apparent that various modifications may bemade therein by those;

skilled in the art. For example, While the insulating member between thebase and the normally stationary contact, in each of the switchesillustrated in Figs. 1 through 9, has been shown as a strip or plate ofmaterial extending substantially the length of the base and also servingto insulate the latter from the mounting means for the thermalresponsive member and the movable contact, it will be apparent thatseparate insulating washers may be employed for this purpose or the baseitself may be formed of insulating material so that separate insulatingwashers or members are not necessary as is shown in Fig. 16.Furthermore, while various arrangements of spacing collars andinsulating washers have been illustrated for effecting the desiredspacing and/ or insulation of the various elements of the switches itwill be apparent that the thicknesses of these insulating washers and/orcollars may be varied as desired and the separate collars and insulatingwashers may be replaced by insulating collars of suitable size.

In each of the forms of the switches disclosed in the drawings thethermal responsive members have been indicated as electrically insulatedfrom the contacts of the switch. This is to prevent electrical currentfrom flowing through the thermal responsive member which current mightresult in altering the operation thereof due to the heating effectproduced thereby. In some instances, however, it is desirable that thisheating efiect be provided in a thermostatic switch and this may bereadily effected, in accordance with the constructions here illustratedand described, by simply omitting the insulation between certain of theparts as will be readily apparent to one skilled in the art.

While each of the forms of switches disclosed in the drawings have beenso constructed that the contacts thereof are normally in engagement fortemperatures below a predetermined value, and are separated attemperatures equal to or above a predetermined value, it will be readilyapparent that the principles of this invention may be readilyincorporated in switch constructions operating in the reverse manner.That is, the switches may be so made that the contacts are normally inopen position below a predetermined temperature and are operated intoengagement at temperatures canal to or above predetermined temperatures.Moreover, while the thermal responsive members have been here indicatedas employed for operating electrical switches it will be apparent thatsimilarly constructed elements may be advantageously employed in thermalresponsive devices other than electrical switches. These, as well asother changes and adaptations are contemplated as included within thebreadth of the present invention which is intended to be limited only bythe breadth and scope or the appended claims.

Having thus described my invention, I claim:

1. A thermostatic switch comprising a rigid base member, an electricalcontact rigidly mounted upon and insulated from said base member, anelongated resilient member, an elon ated bimetallic member, a commonmeans mounting one end of each of said resilient and bimetallic membersupon said base member in superposed alignment with the bimetallic memberbetween said base and resilient members, means cooperating with saidmounting means to vertically space said resilient and bimetallic membersfrom each other and from said base member, an electrical contact carriedby the other end of said resilient member for engagement with the firstmentioned contact, the said bimetallic member including a main portionextending substantially parallel with said resilient member and anintegral extension of length sufficient to provide for appreciableflexing thereof disposed at substantially right angles to said mainportion and directed towards said resilient member so that flexing ofsaid bimetallic member in response to variations of temperature causesthe outer end of said extension to exert both substantiallyperpendicular and longitudinal forces on the resilient member with thesaid longitudlnal force producing friction between said ex tension andsaid resilient member such that flexing of the bimetallic member isprevented from causing movemnt of said resilient member until the saidflexing has stored sufiicient energy in the bimetallic member toovercome the static friction whereupon the resilient member and itscontact are moved with a snap action relative to the first mentionedcontact, and means adjustably mounted on said base member and engagingthe main portion of said bimetallic member intermediate its ends toprovide an adjustable abutment for the latter thereby regulating theoperation of said switch.

2. The combination as defined in claim 1 and in which the means formounting said bimetallic member comprises a hinged connection betweensaid bimetallic member and the said mounting means.

3. The combination as defined in claim 2 and in which the said hingedconnection includes a pair of diametrically extending ears upon saidhimetallic member received in cooperating recesses in a portion or" themounting means.

A thermostatic switch comprising a base member, a first electricalcontact mounted on said base member, a second electrical contact, anelongated resilient member supporting said second contact on said basemember for movement in opposite directions relative to said firstcontact and normally biasing said second contact for movement in one ofsaid directions, a unitary elongated bimetallic member having twointegral portions extending in directions at substantially right anglesto each other, means supporting said bimetallic member intermediate saidbase and resilient member with one of said portions extendingsubstantiall parallel with said resilient member in superposed alignmenttherewith and with the other of said portions directed towards andadapted to engage said resilient member, the length of said otherportion of the bimetallic member being in the order of one-third thelength of said one portion thereof, and adjustable means mounted on saidbase and adapted to engage said one portion of the bimetallic memberintermediate its ends, whereby variations in temperature cause both ofsaid portions of the bimetallic member to flex thereby exerting bothsubstantially perpendicular and longitudinal forces upon said resilientmember with the said longitudinal force producing friction between theend of said other portion of the bimetallic member and the adjacentsurface of the resilient member so that flexing or" the bimetallicmember is prevented from causing movement of the resilient member untilthe said bimetallic member has stored sufiicient energy therein byflexing of both of the said portions thereof to overcome the staticfriction whereupon the said bimetallic member moves said resilientmember and the said second contaicjt relative to the said first contactwith a snap ac ion.

CHARLES S. MERTLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,970,224 Cole Aug. 14, 19342,020,538 Dennison Nov. 12, 1935 2,103,181 Richmond Dec. 21, 19372,109,848 Olds Mar. 1, 1938 2,158,850 Campbell May 16, 1939 2,200,557Kuhn et al May 14, 1940 2,267,387 Winborne Dec. 23, 1941 2,298,928 Clarket a1 Oct. 13, 1942 2,317,033 Dafforn Apr. 20, 1943 2,409,420 Clark Oct.15, 1946 2,476,083 Clark July 12, 1949

